Radio system for locating objects



Patented July 6, 1937 PATENT OFFICE RADIO SYSTEM FOR LOCATING OBJECTSErnst Gerhard, Berlin, Germany, assignor to Telefunken Gesellschaft fiirDrahtlose Telegraphic in. b. H., Berlin, Germany, a corporation ofGermany Application'June 12, 1936, Serial No. 84,786 In Germany June 8,1935 8 Claims.

The present invention relates to a system and a method suitable fordetecting or locating distant objects by the aid of ultra-short waves.

It is known that by the aid of a combination of transmitter and receiverinstruments, separated one from another by a known distance, distantobjects having reflecting properties may be located. Use is made oftriangulation methods. The antenna connected to the transmitter iscaused to propagate waves in a sharply focused beam. The antennaconnected to the receiver has a marked directional characteristic and isadapted to be rotated until a maximum response is obtained. It is thenan easy matter to calculate the distance of the reflecting object fromthe base line joining the transmitter and receiver antennae.

By the methods heretofore practiced, the energy propagated from thetransmitter is usually modulated with either audio frequency or radiofrequency waves or the carrier energy may be keyed on and off. If thecarrier is not modulated but is interrupted, say at a frequency ofsomething like cycles per second, it becomes very difficult to amplifythe signals. If, however, the transmitted energy is modulated with anaudio frequency wave, then difilculties arise in regard to the controlof the energy because both frequency modulation and amplitude modulationare usually present. Erroneous indications are, therefore, apt to begiven.

By another known method the ultra-short wave carrier frequency energymay be modulated by another radio frequency. Here again the samedrawbacks are present that were attendant upon audio frequencymodulation. Still another drawback is encountered in the case ofmodulation with, say, one megacycle with a distance from a reflectingobject of say 1.5 kilometers, since the phase of the modulation wavesreaching the receiver is reversed thereby causing an interferencepattern with the transmitted energy, and thus the waves tend to cancelout and it becomes practically impossible to detect the reflectedenergy.

It is, therefore, an object of my invention to overcome the drawbacks ofthe known systems by providing a new system in which the transmitterpropagates an unmodulated carrier wave 50 and a part of the radiationwhich reaches the receiver directly from the transmitter is modulatedand combined with the reflected unmodulated energy so as to producesatisfactory signals in the receiver.

55 The invention will now be explained in further detail, referencebeing made to the accompanying drawing in which Fig. 1 showsdiagrammatically one embodiment of my invention including transmittingand receiving apparatus and a modulator associated with the receiver;

Fig. 2 shows a different embodiment of the invention in which themodulator has its own antenna system located so as to receive andretransmit waves in between the transmitter and the receiver; and

Fig. 3 shows still another modification in which the modulator isprovided with two antenna systems and transmission line for shorteningup the paths of radiation between the transmitter and the receiver.

Referring to Fig. 1, I show an ultra-short wave transmitter I havingconnections to a dipole antenna 8 which is preferably mounted in thefocus of a paraboloidal reflector 9. The energy may then be radiated ina sharply focused beam, the directional axis of which is .indicated bythe line 5. The directional axis may, of course, be oriented suitablyfor exploring a. field and when the beam encounters a reflecting object2 it may be reflected along the axis 6 and be collected by the antenna I0 which is associated with a receiver 3. The antenna [0 is alsopreferably mounted in the focus of a paraboloidal reflector II andclosely adjacent to this receiving antenna i0 is an auxiliary antenna l2which is connected to a modulator I.

It will be seen from the arrangement just described that the energywhich goes out in the direction 5 and is returned in the direction 6represents an unmodulated carrier wave which is relatively free fromdistortion. The modulations from the source I are then locally appliedadjacent the point of reception ill. The combination of carrier wave andmodulated energy may readily be amplified and detected in the receiver3, and hence reliable indications may be made as to the distance anddirection of the reflecting object 2 with respect to a base line 4joining the transmitting and receiving antennae 8 and I0 respectively.

Referring to Fig. 2, the modification of my invention therein shown issimply one in which the modulator I has its antenna l3 located at somesuitable point intermediate between the transmitter and the receiver sothat a portion of the unmodulated carrier frequency energy may be pickedup by the antenna l3 when transmitted along the line I 4.

This energy may then be modulated and rethe unmodulated carrier wave ispropagated along the axis to a reflecting object and is reflected backalong the line 8 thus reaching the antenna is and being combined withthe modulated energy which is received along the line l3. In this case,as in the embodiment previously described, the presence of thereflecting object may readily be ascertained and both its distance andits direction can be calculated from the angles made by the lines 5 and8 with respect to the base line t. a

Referring to Fig. 3, I show still another embodiment of my invention inwhich the modulator l is provided with double conductors l8 and W. Theconductors it lead to an energy collecting antenna, l6 and'theconductors l9 lead to an energy radiating antenna ll. The antenna i6 isadvantageously located with respect to the energy radiated bythe maintransmitting antenna 8. Likewise the retransmitting antenna I! is ad'-vantageously located so as to direct its energy against the receivingantenna Ill. Thus the collection and reradiation of some of the energyfrom the transmitter i may be obtained through the modulator I, whileunmodulated energy is propagated as before along the axis 5, against thereflecting object 2 and then reflected along the axis 6 until it reachesthe receiving antenna Ill.

The modulation frequencies may be chosen at will. The advantage of theembodiments here shown and described resides primarily in the fact thatslight frequency modulations will have no efiect upon the accuracy ofthe direction and distance determinations.

This is true because the path between the. transmitter and the receiverfor energy which'is to be modulated may be made relatively short and thepath of the unmodulated carrier wave which is transmitted to andreceived from a reflecting object; even though it be a long path, isrelatively free from interference and distortion due to the fact thatthe carrier wave is substantially a pure sine wave and can betransmitted and received under conditions of highest eiiiciency.

Various other modifications of my invention may, of course, suggestthemselves to those skilled in the art. It is to be understood,therefore, that the invention itself is limited only in accordance withthe scope of the claims.

' I claim:

1. Radio apparatus comprising a generator of ultra-short waves, meansincluding a directional antenna for radiating said waves in anun-modulated form, a receiver having a directional antenna, means fororienting said antenna into position for maximum reception of areflected beam produced by a distant object in the path of the wavesradiated by the first said antenna, means including an energy collectingand re-radiating device located in the vicinity of said transmitter andreceiver, a modulator in circuit with said device, and means forcombining in said receiver the un-mod ulated waves from said reflectingobject and the modulated waves obtained through said modulator.

2. Apparatus in accordance with claim 1 and having said energycollecting and re-radiating device constituted by a dipole antennaadjacent the directional antenna of said receiver.

3. Apparatus in accordance with claim 1 and having said energycollecting and re-radiating device constituted by a dipole antennalocated in position to receive at least a portion of the unmodulatedenergy from said transmitter and to propagate said energy aftermodulation thereof directly toward the antenna of said receiver.

4. Apparatus in accordance with claim 1 and having said energycollecting and re-radiating device constituted by a two dipole antennaand a pair of conductors feeding energy to and from said modulator.

5. In a device for locating an object within a field of electromagneticradiations, means including an ultra-short wave transmitter having anantenna adapted to propagate an un-modulated carrier wave, a receiverhaving a directional antenna suitably disposed for collecting a portionof said carrier wave which is propagated over a path including a surfaceof reflection on said object and for collecting another portion of saidwave which is propagated over a shorter path, means for modulating theenergy received via the shorter path and means for combining theenergies received via the two paths.

6. Radio apparatus for determining the direction and proximity of awave-reflecting object, comprising a transmitter and a receiver, adirectional antenna adapted to radiate unmodulaed energy from saidtransmitter toward said wave-reflecting object, means under control ofsaid transmitter for producing modulated energy, a second directionalantenna adapted to receive superimposed energies from said modulatedenergy producing means and from said wave-reflecting object, and meansfor causing said receiver to make an appreciable response to thecombined reception of modulated and unmodulated energies.

7. Radio apparatus in accordance with claim 6 and having said means forproducing modulated energy arranged to be receptive of a portion of theunmodulated energy from the first said antenna.

8. Radio apparatus in accordance with claim 6 and having a medium ofcommunication of en ergy between the respective antennas of the

